As is known, a problem which is currently strongly felt in the production of diaphragm valves for compressed or liquefied gases relates to the wear of the diaphragm that occurs after a certain number of actuations.
These valves, generally speaking, have a valve body which can be associated with a cylinder of pressurized gas and defines a gas outlet port. A closure port is formed internally, and the gas that arrives from the cylinder passes through it; a gasket acts on said closure port and is supported by a flow control element, which engages in an upward region a diaphragm which in practice closes hermetically the region where the closure port is located.
A pusher piston acts on the diaphragm and can be actuated externally by means of a knob or the like, so as to achieve the translational motion of the flow control element in order to open and close the valve.
The action of the pusher piston on the diaphragm inevitably produces folds and wrinkles arising from the variation of the shape assumed by the diaphragm in the various steps of actuation, and therefore leaks can occur over time.
In order to try to solve the problem, U.S. Pat. No. 4,760,990 discloses a solution in which a plastic washer is provided which, by moving together with the pusher piston, allows to compensate for the major discontinuities but not to eliminate them completely.
Another problem further arises from the fact that rotation of the pusher piston actuation rod inevitably causes rotation of the pusher piston and therefore introduces friction and wear, which are very dangerous for the integrity of the diaphragm.